Reuters news agency reported that she were struggling to stand while she and the newly elected leader in Kiev listened to the national anthem during military honors.
"Since then I have drunk at least three glasses of water -- I obviously needed that and so I'm doing very well now," she told reporters at a press conference with Zelensky. She was no longer shaking at that point.
Berlin experienced high temperatures today, reaching a peak of 86 degrees Fahrenheit (30 degrees Celsius).
CNN's Stephanie Halasz contributed to this report.